Oil well pump jacks in common use today employ a rocking beam referred to as a "walking beam" for reciprocating a vertical pump rod which of course extends into the well to drive the pump. The walking beam is driven from a motor through a gear box which provides the necessary speed reduction. The gear box drives a pair of vertical arms which are connected to the beam to rock the same upon vertical reciprocation of the arms.
Due to the fact that the oil wells are pumped continuously, shocks emanating from the pump rod in the well and from other parts of the system, are transmitted to the drive system. Over a period of time, the shocks may result in breakdown of the gear box and stoppage of the pumping operation. In addition, the gears become worn and develop slack which causes the pump rod to be jerked at the opposite extremes of its strokes, thus making the pumping operation inefficient while placing unnecessary stresses on the pump and other parts of the system.
In addition to the fact that the pumping operations are continuous, they are also often unattended. Hence, when the pump or its rod becomes jammed in the well, the drive system and motor become susceptible to grinding and wear causing damage to the parts and "burn-out" of the motor.